FIG. 1 is a schematic diagram of a structure of a cellular wireless communication system. As shown in FIG. 1, the cellular wireless communication system is mainly composed of a Core Network (CN), a Radio Access Network (RAN) and a terminal.
The CN is responsible for a transaction for a Non-Access Stratum (NAS), such as terminal location update, and is an anchor for a user plane.
The RAN includes a base station, or a base station and a base station controller. The RAN is responsible for a transaction for an access stratum (such as management of radio resources). There may be a physical or logical connection between base stations according to a practical situation, and each base station may be connected to one or more other base stations and may be connected to one or more CN nodes;
A terminal, i.e., a User Equipment (UE), refers to any equipment which may communicate with a cellular wireless communication network, such as a mobile phone or a laptop.
A mobility management unit (a Mobility Management Entity (MME) or a Serving General Packet Radio Service (GPRS) Support Node (SGSN)) is a unit which is located in the CN and is responsible for managing access control, position information update and handover of the terminal. The MME or SGSN is responsible for NAS signalling control from the CN to the terminal and registering the terminal to a network.
A home subscriber information unit (a Home Subscriber Server (HSS) or a Home Location Register (HLR)) is an entity which is located in the CN and is responsible for storing identity information, authentication information, authorization information and other information of the terminal equipment. According to different situations, the HSS or HLR may be used to store the identity information of a user and binding information of the user and the terminal equipment, or only store the identity information of the user (the binding information of the user and the terminal equipment may be stored by a gateway), or directly store identity information of the terminal equipment. The HSS or HLR is also responsible for a subscription database of the user, and performing authentication and authorization on the user. A service platform may inquire user or terminal information from the HSS or HLR.
A Machine Type Communication Inter Working Function entity (MTC IWF) is a connection entity between a mobile communication network and an external public network, which can implement protocol conversion, address inquiring, information storing and other functions. The IWF entity is connected to an application server externally, and may be connected to the HSS/HLR or MME/SGSN internally.
Generally, for some services, such as a monitoring and management system needing to acquire monitoring data from a monitor terminal, a terminal needs to be triggered by an MTC application server to establish a connection of the terminal and the MTC application server, so as to report required data. Then, after receiving a trigger message from the MTC application server, the terminal needs to be able to immediately response to establish the connection of the terminal and the MTC application server. At present, in order to satisfy a requirement of the MTC application server for triggering the terminal, in existing solutions, a trigger message is sent to an HSS via a server, the HSS inquires the MME/SGSN of a service terminal and sends the trigger message to the MME/SGSN, then the MME/SGSN sends the trigger message to the terminal through an NAS signalling, and the terminal establishes a connection of the terminal and the server according to the trigger message.
In the existing solutions, the MME or SGSN may reject an NAS request message initiated by a terminal which is under congestion control, and include a back-off timer in a rejection message such that the terminal cannot initiate any request until the back-off timer expires. However, since the existing network may remove the corresponding terminal trigger message after an effective timer related to the terminal trigger message expires, before the back-off timer of the terminal expires and after the effective timer related to the terminal trigger message expires, the existing network may remove the corresponding terminal trigger message, such that the terminal fails to be triggered.